The Electronic and Interface Materials Lab aims to understand and develop functional thin-films, device contacts and electrodes, and applied nanomaterials that can improve next-generation optoelectronic devices and integrated circuits.
Our focus lies on the dynamics of charge carriers in metal-dielectric and dielectric-semiconductor interfaces. Such interfaces are fundamental to the operation of most electronic devices, from simple diodes and solar cells to complex 2D field effect transistors and memories. We explore a range of functional materials which can serve as a platform for tailoring and controlling semiconductor devices. Most notoriously we work in materials that can improve the conversion efficiency of photovoltaic devices. It is our aim to promote the uptake of solar electricity generation throughout the world and in this way contribute to the mitigation of climate change.
This young group was established in 2019 by Dr Ruy Sebastian Bonilla. It brings together our previous world-leading work in silicon photovoltaics, with a broadened research scope on applied thin-film materials and interfaces, the manufacturing of contacts and electrodes, and the exploitation of nanomaterials for enhanced device performance. These topics are supported by advanced characterisation techniques and modelling algorithms we have developed in house. We're happy to engage in new areas where semiconductor-dielectric interfaces can affect or limit device performance, so please drop us a line if you'd like to collaborate.
Sustainability evaluations on material consumption for terawatt-scale manufacturing of silicon-based tandem solar cells
Progress in Photovoltaics, Research and Applications, 2023,1–13
Here we show that III-V, CIGS and CdTe are unsuitable for TW-scale solar manufacturing. Si-Pvk tandems the most sustainable as long as indium is not required. Additionally, while tandem cells can reduce silver consumption / kW, the PERC cell architecture could allow for significantly reduced Ag consumption compared with both TOPCon and SHJ.
On the kinetics of high intensity illuminated annealing of n-type SHJ solar cells: 0.4%abs efficiency gain in one second
Solar Energy Materials and Solar Cells, 248, 2022, 112039
Silicon heterojunction solar cells have achieved world record high efficiencies and have thus gained the interest of solar cell manufacturers. Here we show that light soaking of silicon heterojunction cells increases their efficiency by 0.4% absolute in just 1 s. This process is short enough to be incorporated into mass production to enhance the power output of SHJ modules.
Towards accurate atom scale characterisation of hydrogen passivation of interfaces in TOPCon architectures
Solar Energy Materials and Solar Cells 246, 2022, 111915
We use atom probe tomography to image hydrogen at the critical interfaces in TOPCon solar cell architectures. We present 3D atom maps of the layered structure and discuss the difficulties associate with accurate mapping of hydrogen.
Electrostatic Tuning of Ionic Charge in SiO2 Dielectric Thin Films
ECS Journal of Solid State Science and Technology, 2022 11 063010
Here we show the successful incorporation of K+, Rb+ and Cs+ ions into SiO2 thin films using an electric field and temperature-assisted embedding process. A comprehensive model of ion migration has been developed to show the dependency of ion kinetics on temperature and surface fields.
Extracting band-tail interface state densities from measurements and modelling of space charge layer resistance
Solar Energy Materials and Solar Cells, 2021 (Top Silicon PV conference contribution)
Here we describe a new method to estimate the interface state density at band tails in dielectric-semiconductor interfaces. For this we use sheet resistance measurements and TCAD predictions of conductivity in space charge layers.
Unravelling the silicon-silicon dioxide interface under different operating conditions
Solar Energy Materials and Solar Cells, 2021
Here we investigate the recombination at the Si-SiO2 interface by varying temperature, injection-level, and dielectric charge. Using the extended Shockley-Read-Hall recombination model we provide the first report of the interface defect parameters as a funciton of temperature, including an observation of temperature-dependence in the capture cross-sections.
Recombination in Passivating Contacts: Investigation Into the Impact of the Contact Work Function on the Obtained Passivation
Solar RRL, 2201050, 2023
Improving contacts in silicon solar cells is crucial for reaching high-efficiency and low-cost solar electricity. Here we study the impact of the metal work function on the contact electrical characteristics. The surface saturation current density is extracted from photoluminescence and simulated to gain insights into the interface charge dynamics. Suitable metals should be deployed to minimise losses in high-efficiency solar cells.
SiNx and AlOx Nanolayers in Hole Selective Passivating Contacts for High Efficiency Silicon Solar Cells
IEEE Journal of Photovoltaics, vol. 13, no. 1, pp. 22-32, 2023
Maximising the efficiency of silicon solar panels requires the use of passivating contacts with nano-interlayers that limit the loss of charge at silicon/metal interfaces. Here we investigate silicon nitride and aluminium oxide as novel nanolayers that provide passivation while allowing charge flow. We show that these nanolayers have significantly lower resistivity than current standard silicon oxide. A promising reduction in loss was shown with the AlOx interlayer, in part due to the dielectric intrinsic high negative charge.
Full-Area Passivating Hole Contact in Silicon Solar Cells Enabled by a TiOx/Metal Bilayer
ACS Applied Energy Materials, 2022, 5, 10
This work presents a titanium oxide nanolayer contact grown by atomic layer deposition that provides efficient passivation and hole extraction with high optical reflectivity at the rear of Si solar cells. Proof-of-concept solar cells with either a p- or an n-Si absorber demonstrate 20% efficiency, exhibiting a higher infrared response compared with the conventional rear contacts.
Observations of contact resistance in TOPCon and PERC solar cells
Solar Energy Materials & Solar Cells 246 (2022) 111934
This work presents observations of hydrogen induced contact resistance in PERC and TOPCon solar cells, where the contact resistance has been isolated to occur at the Ag/n+ Si interfaces, and respond differently to applied biases. These insights are critical to the understanding of degradation in industrial solar panels.
Modelling of Kelvin probe surface voltage and photovoltage in dielectric-semiconductor interfaces
Materials Research Express, 9 (2022) 085901
In this work we report a theoretical model to interpret Kelvin probe surface voltage and photovoltage measurements including four critical mechanisms: charge stored in interface surface states, charge in different locations of a surface thin film, changes to effective lifetime and excess carrier density, and the non-uniformity of charge.
Assessing the Potential of Inversion Layer Solar Cells Based on Highly Charged Dielectric Nanolayers
physica status solidi (RRL) – Rapid Research Letters, 2021
In this work we study the production and performance of inversion layer silicon solar cells. An ion‐injection technique is used to obtain highly charged dielectric nanolayers, with charge densities as high as 2 × 1013 cm−2. On the basis of such high chage, an efficiency of 24.8% on 10 Ω cm silicon substrates is predicted. Better performance is expected with enhanced passivation, higher charge densities, and optimal negative charge at rear dielectric.